Chop cherries roughly and place in the bowl of an electric mixer with a whisk attachment.

Whisk on medium speed for a few minutes to break up. Add sugar and egg whites and whisk on high speed for five minutes, until more than doubled in volume.

Place mixture in a one-litre container and freeze for four hours, or overnight.

Note: Fresh cherries can be frozen. Wash first, then dry and freeze in an airtight container for up to six months.